The overall long-term goal of this Program is to define the key components in signaling pathways from the cell surface to the nucleus which lead to distinct fates in lymphocytes such as new gene expression, cell maturation, proliferation or cell death. Lymphocytes have been selected for study since 1) lymphocyte maturation pathways are relatively well-defined, 2) lymphocytes have a set of very well-defined surface receptors, 3) the tools and methods are available for altering lymphocyte signaling pathways both in vitro and in vivo, 4) signaling pathways through antigen receptors and certain cytokine receptors have been characterized in lymphocytes, and 5) there are well-defined models in lymphocytes for monitoring early signaling processes, gene expression and cell death. Initial signaling through the B cell antigen receptor complex (BCR) involving the protein tyrosine kinase (PTK) Syk and the B cell-specific surface receptor CD22 will be elucidated in Clark's Project. Syk has recently been found to associate with the BCR and CD22 and its role in initiating downstream signaling pathways will be identified. Hockenberry's project will examine events proximal to crosslinking surface IgM BCR on B cells leading to activation-induced cell death. The role of bcl-2 and related proteins in affecting cellular oxidants and cell death will be examined. Another set of early events induced after crosslinking lymphocyte surface receptors is the initiation of the protein kinase cascade called the MAP kinase pathway. Guanine nucleotide binding proteins encoded by the c-ras protooncogenes have recently been shown to function upstream from the MAP kinase pathway. Thus Kreb's project will focus on defining the regulation of p21/ras and MAP kinase cascade-associated kinases in T lymphocytes activated by interleukin-2 or the key T cell accessory receptor CD28. The role of the MAP kinase cascade in affecting the fate of B cell apoptosis or T cell anergy will also be investigated. Recently a novel cytokine-induced 85 kDa nuclear protein kinase has been identified in B lymphocytes and other cells. Bomsztyk's project will purify and clone cDNA encoding this kinase and identify the cellular effectors which activate the 85 kDa kinase. The role of the 85 kDa kinase in affecting cell fates regulated in the nucleus such as gene transcription will be examined. The cytokine interferon-gamma (IFN) like lipopolysaccharide (LPS) can activate B lymphocytes and induce new expression of lymphocyte-associated genes encoding molecules such as kappa light chain or the B cell surface molecule, CD40. Sibley's project has isolated B cell mutants which fail to respond to LPS or IFN and will focus on identifying the lesions in four mutants of the 70Z/3 line. Using these mutants, the Project will also define how the pathways leading to kappa vs. CD40 expression intersect and differ. The projects will make use of transgenic mouse lines, e.g., overexpressing active enzymes or expressing inactive kinases. Thus, the Program will utilize a Transgenic Mouse Core for common development and use of transgenic mice. The common systems, signaling pathways and overall goals of the Program unify the Projects into a cohesive whole. This Program will provide new insights into how the activation and fates of lymphocytes and cells in general are regulated.